The invention relates to a vacuum distributor box of the type having a suction connection and several vacuum connections, the vacuum connections accommodating selective connection of vacuum lines which open one way valves when inserted.
A vacuum distributor box of the relevant generic type is described in German Published Unexamined application (DE-OS) No. 2,617,132. It has several vacuum connections which are connected, in groups, to a common vacuum chamber and which cannot be closed off from one another within the groups. For the selective connection of a test tool, each of these groups have assigned to it a further (test) vacuum connection which can be closed off from the vacuum chamber by means of a non-return valve. This non-return valve is prestressed against its sealing seat with such a high spring force that even the maximum differential-pressure force occurring as a result of the vacuum on the chamber side and the atmospheric pressure from outside cannot open it counter to the spring force. Only as a result of mechanical action, in particular the insertion of the vacuum line of the test tool, is the non-return valve opened, thus freeing the respective vacuum connection. When the line is removed again, the non-return valve closes immediately.
Such non-return valve safeguards for fluid connections are also known for plug-in hose or pipe couplings (for example, see German Patent DE-PS 683,540). However, the disadvantage common to the known designs is that a relatively high outlay for sealing off the non-return valves, on the one hand, and the insertable fluid connections, on the other hand, is necessary. In vacuum distributor boxes with groups of vacuum connections to common vacuum chambers, all the vacuum connections of a group must also be occupied, hence inoperative connections are occupied, for example, by additional dummy plugs, in order to prevent a vacuum connection left free and the common vacuum chamber from causing the other connections of the group to be vented.
An object of the invention is to design a vacuum distributor box of the relevant generic type, so that, without additional measures, variable numbers of vacuum lines can be connected to common vacuum chambers at only a low outlay for sealing off the vacuum connections and vacuum lines.
This object is achieved by making the housing of the vacuum distributor box in two parts sealed off relative to the outside by an elastic diaphragm seal clamped between the two housing parts. This diaphragm seal is provided with a number of perforations in the respective mouth region of the vacuum connections, the diaphragm sealing faces serving on the one hand as valve sealing seats for a non-return valve at the respective vacuum connection and as annular seals for a connected vacuum line.
Other advantageous developments of the vacuum distributor box according to the invention includes provision of a respective non-return valve which also operatively engages the diaphragm seal.
When each individual vacuum connection is equipped with a non-return valve, by means of the claimed design the outlay for sealing off the housing of the vacuum distributor box, the non-return valve seats and the vacuum lines to be inserted is greatly reduced in an advantageous way because a one-piece diaphragm seal is clamped on all sides between the two housing parts and also has perforations, the number and position of which correspond to the number and spatial arrangement of the vacuum connections. At the same time, the edges of the perforations on the one hand form the valve sealing seats for the non-return valves and on the other hand come sealingly up against inserted vacuum lines. The diaphragm seal thus, in one piece, performs three sealing functions simultaneously. The number of seals to be used and of the number precision-machined sealing faces in the housing is markedly reduced, and it therefore also becomes much simpler to assemble the vacuum distributor box.
In the generic state of the art represented by German Published Unexamined Application (DE-OS) No. 2,617,132, the common vacuum chambers of the vacuum connections are each protected against the penetration of ambient pressure from the suction side by means of a protective valve. In an advantageous development of the vacuum distributor box according to the invention, this sealing function can be the fourth one performed by the diaphragm seal.
Admittedly, it is already known to form a non-return protection valve of a vacuum chamber with several vacuum connections, as a concertina segment, in a diaphragm seal which is clamped between two housing halves, see German Published Unexamined Patent Application (DE-OS) No. 3,031,625. Nevertheless, the known arrangement does not suggest providing the diaphragm seal with further perforations and conveying a suction-air flow through the diaphragm seal three times. Moreover, equipping vacuum connections with non-return valves which can only be opened mechanically as a result of the insertion of vacuum lines cannot be derived from this known design of a vacuum distributor box.
It is now possible to remove, exchange or reinsert vacuum lines even when the vacuum distributor box according to the invention is installed and subjected to a vacuum, without an increase in pressure occurring at the same time in the other vacuum connections or vacuum consumers.
A clip-on connection between the vacuum distributor box and the vacuum lines is conducive to simple handling, whilst the claimed design of the non-return valve bodies as cones with recesses makes it possible to use conventional pipe ends on the vacuum lines, without approximately centrally arranged actuating tappets or the like having to be provided for pushing back and opening the non-return valves, as applies, for example, to the connections of tyre-pressure test instruments.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.